In the fabrication of mechanical structures such as aircraft, it may be necessary to introduce fillers between interfacing surfaces of the component parts to assure proper and safe structure. Fillers (also known as shims) are pieces of metallic or non-metallic materials which are placed in gaps between the component parts to compensate for dimensional variations or tolerance buildup between the parts. In the aircraft industry, fillers may be used in fitting and joining major structural sections to one another and throughout substructures as they are built-up into a full aircraft structure. The use of fillers may compensate for dimensional variation between parts or bring parts into proper alignment.
A conventional method of defining and producing custom fillers may include measuring gaps between parts using feeler gauges, capacitive gap measuring instrumentation or computer/laser based scanning measurement systems. The gap measurement data may be documented and delivered via entry into a series of software capabilities which process the gap measurements, updated digital definitions of the fillers and generates portable Machine Control Data (MCD). The MCD is downloaded to a central server which delivers the MCD to a Computer Numerical Control (CNC) controlled machine tool. The CNC machine tool machines the filler using cutting tool configurations which are specific to the filler and its material being manufactured. Following the machining of the filler on its surface and profile, it is de-burred and the filler marked with its identification to facilitate its installation in the structure.
In previous applications, the conventional filler definition and elements of the production process may be paper-based. In some production schemes, however, the full design definition of the structure which is being fabricated may be digitally defined and electronically stored and processed in a CAD/CAM system such as CATIA V5 and Enovia. For large-scale production of aircraft, the design definition of an aircraft may be defined by engineers from many companies which design various sections of the aircraft. That digital definition establishes and maintains the full definition of all components in their spatial relationship—in aircraft coordinates. The fabricated aircraft sections undergo final assembly at an aircraft assembly plant.
In current aircraft production schemes, an automated process of defining, producing and tracking the status of custom fillers on demand for immediate installation on an inline flow production line when the full design definition of a structure resides in a CAD/CAM system is required.